1. Field
Example embodiments relate to a memory device driving circuit for driving a resistive memory device capable of having two or more states in accordance with a variation in resistance and a method of fabricating the same. Other example embodiments relate to a memory device driving circuit which may include a secondary driver connected to a memory device including a memory layer arranged between a first electrode and a second electrode, to control a set resistance of the memory device and a method of fabricating the same.
2. Description of the Related Art
In accordance with recent development of data compression and transmission techniques, development of new electronic appliances (e.g., portable terminals, various smart cards, electronic cash, digital cameras, memories for games, MP3 players and/or multimedia players) has increased. Such new electronic appliances may be configured to use an increased amount of information. The demand for various memory devices capable of storing an increased amount of data may have also been increased. Increased use of portable information appliances may have increased the demand for a memory device having non-volatile characteristics preventing or reducing recorded information from being erased even in a power-off state. Most memory devices may include a bistable element which is switchable between a higher resistance state and a lower resistance state upon receiving a voltage. Resistive memory devices, which have a concept compared to capacitive memory devices, may include a memory that varies in resistance in accordance with a voltage applied thereto, and may store data corresponding to the resistance variation.
Chalcogenide materials, semiconductor, and various oxides and nitrides may have resistive memory properties. Organic materials may have resistive memory properties. Resistive memory devices may have drawbacks of increased driving voltage and current, decreased durability and decreased thin film handling properties. Because such drawbacks have been overcome in accordance with recent developments of material engineering, resistive memory devices may be currently non-volatile, lower-power, higher-density, and multi-bit operating memories. Examples of such a resistive memory device may include a phase change RAM, an organic memory, an oxide resistive RAM (OxRAM) and/or a metal filament memory.
The resistive memory device will be described in conjunction with, for example, the organic memory. The organic memory may include an organic memory layer between an upper electrode and a lower electrode. Memory cells providing bistability characteristics may be formed at points where the upper and lower electrodes cross each other.
The memory cells of the resistive memory device may have two states, namely, a set state corresponding to a lower resistance state and a reset state corresponding to a higher resistance state. When it is assumed that data of “1” corresponds to the lower resistance state, and data of “0” corresponds to the higher resistance state, two logic states of data may be stored.
In such a memory device, read-out of data may be carried out as follows. One bit line and one word line may be selected from a memory matrix, to select a specific memory cell. Thereafter, current may be supplied from the outside of the memory device to the specific memory cell. A voltage variation may occur in the memory cell in accordance with the resistance state of the organic memory layer in the memory cell. In accordance with the voltage variation, data of “0” or “1” may be read out.
In most memory devices, however, an accurate read out of the voltage variation may be difficult unless a separate amplifier is used, because the resistance in the set state may be relatively small. The configuration of such a memory device may become complex. The resistance in the set state may be non-uniform. Errors may be generated during the operation of the memory device for reading the memory cell.